GH1:
I have not found mention of this lancemate bug but I could have failed my search skill roll:
I had recruited the combat medic, but shortly after, he told me he could no longer carry on working with me (it is a little strange, as it happened during a battle, and he was still registered in my roster during it, with Shift-H, but was not available, and sent a message saying he had to leave right after the battle).
Even though his disappearance is somewhat strange (there was no prior notice, and I was playing as a pretty lawful and honorable guy, with a high leadership skill), the main problem is that he knows "haunts" the world map, and appears as a hostile character (red dot) I can attack in the world map itself.